"The PS/2 Interface is quite easy to implement. To send a key stroke, the keyboard begins driving the clock line. On the falling edge of the clock line, the data line represents the current bit. Each keystroke is sent as 11 bits: first a start bit of 0, then the 8 bits of the scan code (least significant bit first), then a parity bit (odd parity, which we did not implement for simplicity’s sake), and finally a stop bit (always 1)."